AF A ® www.afa.org.uk The heart, the pulse and the electrocardiograph Providing information, support and access to established, new or innovative treatments for atrial fi brillation www.afa.org.uk Registered Charity No. 1122442 Glossary Arrhythmia Heart rhythm disorder Contents Arrhythmia Nurse Specialist A nurse who is Glossary trained in heart rhythm disorders The heart Atrial Fibrillation (AF) An irregular heart rhythm due to a rapid, disorganised electrical disturbance of The pulse the heart’s upper chambers (the atria) How to take a pulse Atrial Flutter (Afl ) A rhythm disorder of a more organised electrical disturbance in the heart’s upper The electrocardiograph chambers. The heart rhythm may be either regular (ECG) or irregular Bradycardia A rhythm disorder characterised by a slow heart rate of less than 60 beats per minute Cardiologist A doctor who specialises in the diagnosis and treatment of patients with heart conditions Echocardiogram An image of the heart using echocardiography or soundwave-based technology. An echocardiogram (echo) shows a three dimensional shot of the heart Electrocardiograph (ECG) A 2D graphic of the heart’s electrical activity. An ECG is taken from electrodes on the skin surface Heart Failure The inability (failure) of the heart to pump suffi cient oxygenated blood around the body to meet physiological requirements Sinus Rhythm Normal behaviour of the heart Syncope Fainting/passing out from a temporary lack of oxygen going to certain areas of the brain Tachycardia A rhythm disorder characterised by a rapid heart rate of more than 100 beats per minute 2 The heart The heart Structurally, the heart consists of two sides, a right and normal and a left. The right side pumps the blood through conduction the lungs to collect oxygen before travelling to Vena the left side of the heart. From here it is pumped Cava through the body, to return eventually to the right side once more. Both sides of the heart Pulmonary Veins contract at the same time in a single coordinated action to produce a heart beat. Sinus Node Each side of the heart is separated into two chambers, the atrium (upper chamber); receiving Atrium blood to the heart and the ventricle (lower AV Node chamber); pumping blood away from the heart. Conducting The atria collect the blood from the body on the pathways right side of the heart through a large vein called Ventricle the vena cava and from the lungs on the left side of © 2012 AF Association the heart through four pulmonary veins which all (Figure 1) enter the left atrium close together. Once fi lled with blood, the atria contract and force the blood into the ventricles. The atria and ventricles on both sides of the heart are separated by valves made up of thin fi brous tissue. The valve on the right side is called the tricuspid valve and the valve on the left is the mitral valve. As the ventricles contract, these valves are forced closed, preventing the backfl ow of blood to the atria. With the tricuspid and mitral valves closed, the blood is pumped from the ventricles around the body, through arteries. On the right side of the heart this artery is called the pulmonary artery which takes blood to the lungs. On the left this artery, the largest artery in the body, is called the aorta. 3 The heart is myogenic, meaning it can initiate its own heartbeat. The sequence of events which make up a heart beat is known as the cardiac cycle. Once fi lled with blood, the atria receive an electrical impulse from the sino-atrial node (SA node). This electrical impulse spreads from the SA node over the walls of the atria and causes it to contract – forcing the blood out of the atria and into the ventricles (bottom chambers of the heart). Whilst the ventricles are fi lling with blood, the impulse sent from the SA node is recognised by a second region of the heart known as the atrioventricular node (AV node). The AV node then sends its own electrical impulse over the walls of the ventricles, causing them to contract and for blood to get pumped around the body. Because the SA node controls and coordinates the heart beat, the natural heart rhythm is known as ‘sinus rhythm’. The pumping action of the heart must allow time for the blood to move from the upper chambers to the lower chambers and then out into the rest of the body. If the heart goes too slowly (bradycardia) then the output of blood can be insuffi cient to supply the body’s needs. Bradycardia can make someone feel light-headed or tired, and even faint. If the heart goes too rapidly and there is not enough time for the bottom chambers to fi ll up properly, then, once again, the output of blood can be insuffi cient to supply the body’s needs. In this case you can feel tired and breathless as the body’s demands are greater than the supply. For patients diagnosed with atrial fi brillation (AF) the sinus node no longer controls the rhythm of the heart. Many diff erent parts of the atrial chamber contract at several diff erent times. This makes the contraction of the upper chambers disorganised and ineff ective. It is important to note that while the atrial contraction has some impact on the heart’s action as a pump the majority of the blood fl ow into the ventricle is passive and so patients who are in AF need not be unduly concerned about problems arising due to the atria contractions being interrupted. 4 The pulse The pulse indicates the heart rate and the heart rhythm. Being aware of your pulse is important because it may indicate an abnormal heart rate or rhythm. The pulse can be taken in several points on your body, two of the easiest places are: On the neck: below the On the wrist: between earlobe between the the end of the thumb muscle of the neck and and where a watch strap the wind pipe (carotid would rest (radial pulse) pulse) In a First Aid situation, the pulse lets you know if the heart is beating. Ideally it should beat in a rhythm, like the ticking of a clock; occasionally it may miss a beat, but in general, this is normal. However, if your pulse has no pattern, then it is said to be irregular and should be checked by your doctor. 5 How to take a pulse Taking a pulse: The easiest way to detect atrial fi brillation • Using three fi ngers, place them on the inside of The pulse should the wrist between the watch strap and the base have the rhythm of of the thumb a ticking clock. • Keep fi rm pressure on the wrist with your fi ngers in order to feel the pulse • The rate of the pulse can be found by counting for a minimum of 15 seconds and multiplying by four, better 30 seconds and multiplying by two, this can give the number of beats per minute (bpm) • The heart rate naturally varies, depending on activity and time of day 6 The electrocardiograph (ECG) QRS P ST T PR QT interval Although it was shown in 1774 that an electric current could restore life in the presumed dead, similar to the shocks given in advanced fi rst aid, it took a further one hundred years before Carlo Matteucci, Professor of Physics at the University of Pisa, could show that each heart beat generated an electrical current. In 1887, British physiologist Augustus D. Waller of St Mary’s Medical School, published the fi rst human electrocardiogram, recorded from Thomas Goswell, a technician in the laboratory. 7 Since this time, the ECG has been developed and refi ned to become one of the most important aspects into the investigation of the patient with possible heart related problems. Its spiked graph-like appearance has become an icon of the medical profession, yet is still poorly understood by the general population. When interpreting an ECG, it is important to remember that the contraction of each muscle cell of the heart, generates a small electrical impulse. An example of an It is the recording of these impulses, together ECG machine through receptors placed on the skin, that the ECG pattern is generated. The components of the ECG are labelled P, QRS and T waves. These parts of the pattern show the diff erent parts of the cardiac cycle. The P Wave shows the contraction of the atria and gives a small humped feature. Many clinicians talk about this being the ‘trigger’ of the heart beat when discussing this with their patients. People who have or experience atrial fi brillation at the time of the ECG being performed, will not have co-ordinated contraction of the atrial muscle cells; thus the P wave would be missing. The next point of interest is termed the PR interval. This is the delay caused as the heart’s impulse spreads from the SA node, across the atria walls to the AV node, resulting in ventricular contraction. On the ECG trace this is shown as a gap between the P wave and the sharp peak of the QRS sequence. 8 The classical sharp peak of the ECG is termed the QRS complex. This shows the electrical impulse moving very rapidly through the AV node to the ventricles, causing them to contract and pump the blood out of the heart to form the pulse. Following the QRS complex the ECG becomes quiet From the twelve leads, again with a short fl at line from the fi nal part of the the ECG shows diff erent QRS complex (the S wave) and the following wave, views of the electrical the T wave.